Devices and methods employing dual target auto exposure

ABSTRACT

The method includes automatically adjusting a first control parameter in a device for capturing a first plurality of images, automatically adjusting a second control parameter in the device for capturing a second plurality of images such that automatic adjustment of the first control parameter is interspersed with, separate from, and obtained generally concurrently with the automatic adjustment of the second control parameter. The adjustment of the first control parameter being determined differently compared to adjustment of the second control parameter. The method may include attempting to decode a decodable indicia utilizing one or more images of the first and second plurality of images.

FIELD OF THE INVENTION

The present invention relates in general to image data collection, andin particular to devices and methods employing dual target auto exposuresuch as image sensor based indicia reading terminals.

BACKGROUND OF THE INVENTION

Indicia reading terminals for reading decodable indicia are available inmultiple varieties. For example, minimally featured indicia readingterminals devoid of a keyboard and display are common in point of saleapplications. Indicia reading terminals devoid of a keyboard and displayare available in the recognizable gun style form factor having a handleand trigger button (trigger) that can be actuated by an index finger.

Indicia reading terminals having keyboards and displays are alsoavailable. Keyboard and display equipped indicia reading terminals arecommonly used in shipping and warehouse applications, and are availablein form factors incorporating a display and keyboard. In a keyboard anddisplay equipped indicia reading terminal, a trigger button foractuating the output of decoded messages is typically provided in suchlocations as to either enable actuation by a thumb of an operator or insome cases also providing a handle and trigger button that can beactuated by the index finger.

Indicia reading terminals in a form devoid of a keyboard and display orin a keyboard and display equipped form are commonly used in a varietyof data collection applications including point of sale applications,shipping applications, warehousing applications, security check pointapplications, and patient care applications, and personal use, commonwhere keyboard and display equipped indicia reading terminal is providedby a personal mobile telephone having indicia reading functionality.

Some indicia reading terminals are adapted to read bar code symbolsincluding one or more of one dimensional (1D) bar codes, stacked 1D barcodes, and two dimensional (2D) bar codes. Other indicia readingterminals are adapted to read optical character recognition (OCR)characters while still other indicia reading terminals are equipped toread bar code symbols, OCR characters, postal symbologies or otherinformation bearing indicia.

Bar code symbols are typically disposed on a substrate such as paper.Recently, bar code symbols are now being displayed on a display screen.Attempts have been made to provide indicia reading terminals capable ofreading bar codes on paper and bar codes displayed on a display screen.For example, one attempt includes the indicia reading terminals togglingback and forth between frames with and without the illumination on andeach having custom fixed exposures.

There is a need for further image data collection, and in particular todevices and methods employing dual target auto exposure such as imagesensor based indicia reading terminals.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides a device for obtainingimages which includes an imaging subsystem comprising an image sensorarray and an imaging assembly operative for focusing an image onto theimage sensor array, and a housing incorporating the imaging subsystem.The device is adapted to acquire a first plurality of images based on afirst control parameter in which the first control parameter for asubsequent image of the first plurality of images is adjusted based on aprior image of the first plurality of images, and adapted to acquire asecond plurality of images based on a second control parameter in whichthe second control parameter for a subsequent image of the secondplurality of images is adjusted based on a prior image of the secondplurality of images. The adjustment of the first control parameter beingdetermined differently compared to adjustment of the second controlparameter. The acquisition of the first plurality of images isinterspersed with and obtained generally concurrently with acquisitionof the second plurality of images, and the acquisition of the firstplurality of images and adjustment of the first control parameter beingseparate from acquisition of the second plurality of images andadjustment of the second control parameter.

In a second aspect, the present invention provides an indicia readingterminal which includes an illumination subsystem operative forprojecting an illumination pattern, an imaging subsystem comprising animage sensor array and an imaging assembly operative for focusing animage onto the image sensor array, and a housing incorporating theillumination subsystem and the imaging subsystem. The indicia readingterminal is adapted to acquire a first plurality of images exposedduring illuminated portions of the illumination pattern based on a firstcontrol parameter in which the first control parameter for a subsequentimage of the first plurality of images is adjusted based on a priorimage of the first plurality of images, and adapted to acquire a secondplurality of images exposed during unilluminated portions of theillumination pattern based on a second control parameter in which thesecond control parameter for a subsequent image of the second pluralityof images is adjusted based on a prior image of the second plurality ofimages. The acquisition of the first plurality of images beinginterspersed with and being obtained generally concurrently withacquisition of the second plurality of images, and acquisition of thefirst plurality of images and adjustment of the first control parameterbeing separate from acquisition of the second plurality of images andadjustment of the second control parameter. The indicia reading terminalis operable to attempt to decode a decodable indicia comprising a barcode disposed on a substrate in ambient light using at least one of thefirst plurality of images, and operable to attempt to decode a decodableindicia comprising a bar code disposed on a backlit display using atleast one of the second plurality of images.

In a third aspect, the present invention provides a method for use inobtaining images. The method includes automatically adjusting a firstcontrol parameter in a device for capturing a first plurality of images,automatically adjusting a second control parameter in the device forcapturing a second plurality of images such that automatic adjustment ofthe first control parameter is interspersed with, separate from, andobtained generally concurrently with the automatic adjustment of thesecond control parameter. The adjustment of the first control parameterbeing determined differently compared to adjustment of the secondcontrol parameter.

In a fourth aspect, the present invention provides a method for decodingdecodable indicia. The method includes projecting an illuminationpattern from an indicia reading terminal onto a decodable indicia,automatically adjusting a first control parameter in the indicia readingterminal for capturing a first plurality of images exposed duringilluminated portions of the illumination pattern, automaticallyadjusting second control parameter in the indicia reading terminal forcapturing a second plurality of images exposed during unilluminatedportions of the illumination pattern such that automatic adjustment ofthe first control parameter is interspersed with and obtained generallyconcurrently with the automatic adjustment of the second controlparameter, and attempting to decode the decodable indicia utilizing oneor more images of the first and second plurality of images.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the concluding portion of thespecification. The invention, however, may best be understood byreference to the following detailed description of various embodimentsand the accompanying drawings in which:

FIG. 1 is a schematic physical form view of one embodiment of an indiciareading terminal in accordance with an aspect of the present invention;

FIG. 2 is a block diagram of the indicia reading terminal of FIG. 1;

FIG. 3 is diagrammatic illustration of an imager with a full-frameshutter operating in video mode for use in the indicia reading terminalof FIG. 1;

FIG. 4 is a flowchart illustrating one embodiment of a method fordecoding a decodable indicia using the indicia reading terminal of FIG.1;

FIG. 5 is a timing diagram illustrating one embodiment for decoding adecodable indicia performed by the indicia reading terminal of FIG. 1;and

FIG. 6 is diagrammatic illustration of a series of frames correspondingto the flowchart of FIG. 4 and the timing diagram of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates one embodiment of an indicia reading terminal 1000having a dual target autoexposure capability in accordance with anaspect of the present invention. For example, as explained below, thedual target autoexposure may include separate autoexposure capabilitiesone tailored for reading the decodable indicia such as a bar code 15disposed on a substrate 17 such as paper e.g., attached to a product 19,or device having an electronic paper display, and the other tailored forreading decodable indicia such as a bar code 115 displayed on anelectronic device 120 such as a screen 125 such as a display, monitor,backlit screen, LCD display, or other screen, for example, as a mobilephone, cell phone, satellite phone, smart phone, telemetric device,personal data assistant, and other devices.

As described below, the autoexposure routines may be run generallyconcurrently at the same time and decoupled from each other. Forexample, the indicia reading terminal may be used to obtain a series ofodd images, where the exposure value of a subsequent odd image isdetermined with an auto exposure routine optimized for properlycapturing images of bar codes printed on paper or other non-backlitenvironment, and separately obtain a series of even images where theexposure value of a subsequent even image is determined with an autoexposure routine optimized for properly capturing images of bar codesrendered on a backlit display. As used in herein, the term “image” mayrefer to an image, a portion of an image, image data relating to animage, and a portion of image data relating to an image, and are usedinterchangeably herein.

By adapting terminal 1000 so that each of the autoexposure capabilitiescan be made active responsively to an activation of a trigger signal,terminal 1000 may be rendered as better suited for reading of decodableindicia in an expanded range of operating environments. For example, ifthe decodable image is a bar code on paper or electronic paper, the autoexposure routine used for the series of odd images, may result incapturing images better suited for reading and/or decoding the bar codecompared to the series of even images. If the decodable image is a barcode displayed on a display having its own illumination, the autoexposure routine used for the series of even images, may result incapturing images better suited for reading and/or decoding the bar codecompared to the series of odd images. By interleaving and alternatingbetween the two auto exposure routines, terminal 1000 may improve oroptimize its performance in reading the screen-based indicia andpaper-based indicia, where the decoding of indicia in both situations isdesired

From the present description, it will be appreciated that the presentinvention addresses the problem associated with conventional indiciareading terminals using fixed exposures or fixed image controlparameters in decoding decodable indicia on, for example, cell phoneswhere different cell phones may have different brightness levels andsurface reflectivity which make it difficult to decode the indicia. Inaddition, it will be appreciated that the present invention addressesthe problem associated with conventional indicia reading terminals usingfixed exposures or fixed image control parameters in decoding decodableindicia on a substrate such as paper, or a product where the substrateand the indicia itself may have different colors and surfacereflectivity which make it difficult to decode the indicia.

The following description uses nomenclature associated with indiciareading terminals that may generally include hand held indicia readingterminals or fixed indicia reading terminals optimized for readingprinted or displayed indicia, however those of ordinary skill in the artwill recognize that the present invention is applicable to a variety ofother devices having an imager which may be configured. Examples of suchdevices are: mobile phones, cell phones, satellite phones, smart phones,telemetric devices, personal data assistants, and other devices whichhave imaging capability and are capable of adjusting the configurationof the imager.

FIG. 2 depicts a block diagram of indicia reading terminal 1000, inaccordance with an illustrative embodiment that corresponds with indiciareading terminal 1000. Generally, indicia reading terminal 1000 mayinclude an illumination subsystem 800, an imaging subsystem 900, a handheld housing 1014, a memory 1085, and a processor 1060.

Illumination subsystem 800 may be operative for projecting anillumination pattern 1260 (FIGS. 1 and 2). Imaging subsystem 900 mayinclude an image sensor array 1033 and an imaging optics assembly 200operative for focusing an image onto the image sensor array 1033. Handheld housing 1014 (FIGS. 1 and 2) encapsulates illumination subsystem800 and imaging subsystem 900, in this illustrative embodiment. Memory1085 is capable of storing an image, in which the image data mayrepresent light incident on image sensor array 1033. Processor 1060 isoperative for addressing memory 1085 and processing the frames of imagedata, such as processing for attempting to decode decodable indiciasrepresented in the image data.

FIG. 3 illustrates a basic operation of an imager utilizing a full-frameshutter in video mode, e.g., a mode where frames are constantly beingcaptured. A vertical synchronization signal (VSYNC) 2002 is a signalgenerated by an imager which in this example is active high when a frameof image data is being transferred from the device, and transitionbetween successive frames occurs during the active low period of thissignal. In this diagram, Times A, B, and C represent the transitiontimes between successive frames. Several events occur on or near thistransition time. The first event is that the value of the exposureregister is latched into the imager specifying the time duration of theexposure for use on the next frame. Therefore, any time during a framethe exposure can be written, however at this transition time, theexposure value in the register(s) at that time is latched in for use inthe imager on the next frame. The second event which occurs on thetransition time is that imagers with a full-frame shutter terminate thebuilding of charge on the light sensitive pixels, i.e., the exposurewindow of the imager closes at this point. This is illustrated in FIG. 3by the exposure signal 2004 which is active high during the time whenthe light sensitive array is allowed to accumulate charge. Accumulatingcharge in the light sensitive pixels determines the illumination levelsin the pixels. This accumulating of charge is also referred to as theimage being exposed, or exposing the image and are used interchangeablyherein. The third event which occurs on the transition time is that thecharge built up on the light sensitive array is dumped into a Storageand Transfer array and during the next active high period of the VSYNCsignal the pixel data that was put into the Storage and Transfer arraywill be transferred out of the imager. After the light sensitive arraydata is dumped into the Storage and Transfer array, the light sensitivearray is held at reset to avoid building any charge until the exposurewindow opens and charge is allowed to be gained again for the nextimage.

For simplicity, in the example represented in FIG. 3, the events duringthe transition time are treated as occurring at a single point in time.The actual implementation of an imager may have these events besynchronized at a single point in time, or happen independently across arange of time while the VSYNC signal is inactive. As such, practicalusage of an imager typically treats these events as potentiallyhappening at any time while VSYNC is inactive, and treats a frame asbeing from edge to similar edge of the VSYNC signal. More typically, aframe is treated as being from one active going edge of VSYNC to thenext active going edge of VSYNC.

The timeline of events for a single image in FIG. 3 starts with thewriting of the register value corresponding to Exposure X to theimager's exposure register(s), which is shown as occurring just prior toTime A. At time A, Exposure X is latched into the imager and will be ineffect for the exposing of the light sensitive array during the framebetween Time A and Time B. Immediately after Time A, the light sensitivearray is held in reset until the exposure window opens so that the lightsensitive array can accumulate charge. The time at which the lightsensitive array will be allowed to accumulate charge is Time L. The timeelapse between Time L and Time B is the exposure time of Exposure X, andis illustrated by the exposure signal 2004 being active high betweenTime L and Time B. At Time B, the exposure window closes and the lightsensitive array data is dumped into the Storage and Transfer array.After Time B, the pixel data which was generated with Exposure X, willbe transferred out row by row, and pixel by pixel during the active highperiod of VSYNC between Time B and Time C. It is noticed that theregister value corresponding to Exposure X was written before time A,but the image data generated using Exposure X was only seen beingtransferred from the imager after Time B. An entire frame goes bybetween the writing of Exposure X, and seeing the new image datagenerated with Exposure X. This illustrates the two frame pipeline.

Again, referring to FIG. 3, a feature of the two frame pipeline is thatthe pipeline can be kept full. It is noticed that the writing of theregister value corresponding to Exposure Y to the imager's exposureregister(s), occurs just prior to Time B. So, while the imager wasexposing the pixel array with Exposure X, Exposure Y was written to theexposure register(s). At Time B, the Exposure Y takes effect in theimager, and while the image with Exposure X is being transferred out ofthe imager, the light sensitive array is being held in reset, and thenis allowed to accumulate charge at Time M. The time elapse between TimeM and Time C is the exposure time of Exposure Y, and is illustrated bythe exposure signal 2004 being active high between Time M and Time C. Attime C, the image data generated with Exposure X has completed itstransfer out of the imager, and the image data generated with Exposure Yis dumped into the Storage and Transfer array and after Time C, theimage data generated with Exposure Y is transferred out of the imager.

This sequence of writing of exposure values, and obtaining datagenerated with that exposure value 2 frames later, i.e., the two framepipeline, can be continued indefinitely as long as the imager is poweredand running in a video mode.

By designing an auto exposure routine that evaluates pixel data while itis being transferred out of the imager and then to set an exposure valueon the imager before the end of the frame, the auto-exposure routine hasa 2 frame turnaround. In other words, the auto exposure system evaluatespixel data as it is coming out of the imager, sets a new exposure valuebefore completion of the pixel data being transferred, and the data withthat new exposure value comes out 2 frames later. This means that thespecific auto exposure routine would do the process of sampling, andsetting new exposure values, every other frame. Therefore, two autoexposure routines which can sample and update every other frame can beinterleaved with each other, one routine operating on the odd frames,the other on the even frames.

FIG. 4 illustrates a flowchart of an embodiment of a process 4000 fordecoding decodable indicia in accordance with an aspect of the presentinvention. At block 4002, terminal 1000 (FIGS. 1 and 2) may wait forscanning to be initiated and at block 4006, scanning may be initiated,e.g., by activation of a trigger signal via actuation of trigger 1220(FIG. 1). A trigger signal can also be activated, e.g., via objectdetection, or a serial command from an external computer. Activation mayinclude the powering of the imaging device and/or the enabling of theimager to begin recording image data by allowing the light sensitivepixels accumulate charge.

At block 4010, the system synchronizes to a frame boundary of an imager,and initiates the capture of a frame of image data. This synchronizationis accomplished by monitoring the VSYNC frame synchronization pulse ofan imager. When the VSYNC goes into an inactive state, this indicatesthat the output of frame X has completed and the output of frame X+1 isabout to begin. When this pulse goes inactive, system configurationneeds to be performed to prepare for the output of image data intomemory. Often times this configuration includes setup of a DMA (directmemory access) 1070 (FIG. 2.) and/or other system components for routingthe image frame data into RAM 1080. This needs to be completed beforefor the VSYNC goes active again, or else image frame data could bemissed.

Once synchronization with the imager, and capture initiation have beendone, at block 4012 a determination is made as to whether or not thelast frame data captured was evaluated using a first auto-exposuremethod, referred to as Method A. If not, then while the frame data isbeing captured into memory, at step 4020 the system samples andevaluates the frame data using Method A. Once enough data from thatframe has been evaluated to make a determination, a new exposure valueis calculated at step 4022, and this new exposure value getscommunicated to the imager by configuration of the imager exposureregister(s) at step 4030. In order to run this system optimally, it isimportant that step 4030 finishes while the VSYNC is still active,because typical imager operation is such that the configuration of theexposure value register is latched into the operation of the imager asthe exposure value of the next image at some point while VSYNC isinactive.

Coming back around to 4010, once again the system waits for VSYNC to goinactive indicating that the capture of the last frame has completed,and then initiates capture of another frame in the same way as was donebefore.

Once synchronization with the imager, and capture initiation have beendone, at block 4012 a determination is made as to whether or not thelast frame data captured was evaluated using a first auto-exposuremethod, referred to as Method A. If it has, then while the frame data isbeing captured into memory, at step 4040 the system samples andevaluates the frame data using Method B, which is different in some wayfrom Method A. Once enough data from that frame has been evaluated tomake a determination, a new exposure value is calculated at step 4042,and this new exposure value gets communicated to the imager byconfiguration of the imager exposure register(s) at step 4030. In orderto run this system optimally, it is important that step 4030 finisheswhile the VSYNC is still active, because typical imager operation issuch that the configuration of the exposure value register is latchedinto the operation of the imager as the exposure value of the next imageat some point while VSYNC is inactive.

While the routine described above is explained using distinct anddifferent sampling and/or auto-exposure methods A and B, it will beappreciated that other methods, configurations, or control parametersmay be employed. For example, other methods, configurations, or controlparameters may include different uses of gain, frame-rate, gammacorrection, filtering, windowing the image or sampling the image at alower resolution, and/or other methods which affect the nature of thepixels reported by the imager. Also, other configurations such as theuse of an onboard illumination system 800 during the exposure of aframe, and/or turning off the illumination during the exposure of aframe as explained below is also part of the method being used in thepresent invention. In addition, other methods, configurations, orcontrol parameters may also include different uses of illumination, anaiming pattern, focusing, aperture adjustment, and/or zooming.

In another aspect of the present invention, an indicia reading terminalmay have a light source for emitting an illumination pattern on thedecodable indicia. The illumination pattern may be configurable to beturned on and off. The indicia reading terminal may be used to obtain aseries of odd images with the integrated light source on during theexposure of the pixel array and where the exposure value of a subsequentimage with the light on is automatically adjusted based on a prior imagewith the light source on, and separately obtain a series of even imageswith the integrated light source off during the exposure of the pixelarray and where the exposure value of a subsequent images with the lightoff is automatically adjusted based on a prior image with the light off.

For example, if the decodable image is a bar code on paper or electronicpaper, the series of odd images, captured with the illumination onduring the exposure window, may be better suited for reading and/ordecoding the bar code compared to the series of even images. If thedecodable image is a bar code displayed on a display having its ownillumination, the series of even images, captured with the illuminationoff during the exposure window, may be better suited for reading and/ordecoding the bar code compared to the series of odd images. Byperforming both illuminated and unilluminated exposures, andinterleaving and alternating between the two auto exposure routines,terminal 1000 may improve or optimize its performance in reading boththe screen-based indicia and paper-based indicia, where the decoding ofindicia in both situations is desired, where either illuminated orunilluminated exposures might offer the best conditions for imaging anddecoding the indicia.

In addition, various screen technologies have a wide variety of opticalproperties and may differ widely in reflectivity or other attributesthat optically interfere with successfully imaging a screen undervarious forms of illumination, depending on factors such as theunderlying technology, the number and types of layers involved in orover the screen, whether the screen is color or black and white, orwhether the screen is enabled for touch input, for example. Many typesof screens may cause substantial specular reflection of an externalillumination source, for example. By having an illumination subsystemrefraining from projecting illumination in an exposure period duringwhich an imaging subsystem exposes a frame of image data, the imagingsubsystem may image the target indicia without optical interferenceeffects from the screen such as specular reflection, which may enableterminal 1000 to better image and decode the indicia.

For example, a frame may be captured using a first method such asutilizing illumination (e.g., with illumination subsystem emittinglight) and using a first control parameter such as a first controlexposure parameter or first exposure value. In the initial capturing,illumination may be provided and the first control parameter may be apreset or predetermined first control parameter when using illumination,or the last calculated first control parameter determined usingillumination that was stored in the last triggered scanning.

Illuminated exposure periods and unilluminated exposure periods may beactivated in any order in a reading cycle. For example, the firstexposure in a cycle may be an illuminated exposure and the secondexposure in the cycle may be an unilluminated exposure, or the firstexposure in a cycle may be an unilluminated exposure and the secondexposure in the cycle may be an illuminated exposure, in variousillustrative embodiments.

FIG. 5 illustrates a timing diagram in connection with operation of theterminal 1000 during performance of the method indicated by theflowchart as shown in FIG. 4. Referring to the timing diagram of FIG. 5,a signal 5002 is a trigger signal which can be made active by actuationof trigger 1220 (FIG. 1), and which can be deactivated by releasing oftrigger 1220 (FIG. 1). A trigger signal may also become inactive after atime out period or after a successful decode of a decodable indicia.

Signal 5102 is an input signal to illumination subsystem 800 (FIG. 2)having varying energization levels, e.g., illustrating an illuminationpattern where illumination or light is being alternatively turned on andoff. Periods, 5110, 5120, 5130, 5140 and 5150 illustrate whereillumination is on, and periods 5115, 5125, 5135, and 5145 illustratewhere illumination is off.

Signal 5202 is an exposure signal where active states define periods ofexposing the image sensor array 1033 (FIG. 2) to light and inactivestates intermediate the exposure periods for an image sensor of aterminal. For example, in an active state, an image sensor array ofterminal 1000 (FIG. 2) is being exposed to light incident therein. Anexposure control signal 5202 is an output signal of the imager that isthe result of the exposure configuration for a given frame. The activehigh state of this signal represents the duration of time that the imagesensor array is exposed to light for a given frame of data. As shown inFIG. 5, for example, during exposure periods 5210, 5230, and 5250, theimage sensor array of terminal 1000 is exposed to light incident thereinwhile the illumination subsystem is active. During exposure periods 5215and 5235, the image sensor array of terminal 1000 is exposed to lightincident therein while the illumination subsystem is inactive, e.g., theillumination subsystem is off.

It should be noted that illumination periods 5120 and 5140 do not lineup with any active part of the exposure signal 5202. This is done tomaintain a high frequency duty cycle of the illumination pattern thatavoids flicker while still producing images exposed with and withoutillumination coming from the illumination subsystem.

Signal 5302 is the VSYNC (vertical synchronization) signal otherwiseknown as the Frame Valid signal. The VSYNC control signal is low duringthe transition between frames. During this time, the exposure settingwritten to the imager's exposure register(s) is latched in for usage onthe next frame, the exposure window of a given frame closes, asillustrated by the negative going edge of signal 5202, and also whencharge acquired to the sensor array 1033 (FIG. 2) is put into secondarystorage in preparation of transferring the data out of the device. TheVSYNC control signal is active high when image data from the imagesensor array is being transferred out of the imager's secondary storageinto system memory 1085 (FIG. 2), and in most systems to RAM memory 1080(FIG. 2.) using a DMA 1070 (FIG. 2.) or other system memory routingdevice.

In the timing diagram of FIG. 5, periods 5410, 5415, 5430, 5435 and 5450are periods at which processer 1060 may process frames of the pixeldata, e.g., to determine the quality of the image data. For example,periods 5410, 5430, and 5450 correspond to determination of the qualityof the pixel data resulting from exposure periods when the sensor array1033 (FIG. 2) was accumulating charge while illumination subsystem 800(FIG. 2) was illuminating the field of view of the imager, and periods5415 and 5435 correspond to determination of the quality of the pixeldata resulting from exposure periods when the sensor array 1033 (FIG. 2)was accumulating charge while illumination subsystem 800 was notilluminating the field of view of the imager.

In addition, during the determination of the quality of the pixel data,just at the end of the processing of the pixel data, or at the end ofthe processing of the pixel data, a new image control parameter may becalculated which will be used in subsequent control of the image sensorarray. For example, during period 5410 which is evaluating an imageexposed with illumination subsystem 800 (FIG. 2) illuminating thedecodable indicia, a control parameter CP1 is determined. During period5415 which is evaluating an image exposed with illumination subsystem800 (FIG. 2) not illuminating the decodable indicia, a control parameterCP2 is determined. In one aspect of the present invention, controlparameter CP1 may be used to control the exposure control signal duringperiod 5230, e.g., the next exposure of the array with illuminationsubsystem 800 (FIG. 2) illuminating the decodable indicia, and controlparameter CP2 may be used to control the exposure control signal duringperiod 5235, e.g., the next exposure of the array without illuminationsubsystem 800 (FIG. 2) illuminating the decodable indicia. It will beappreciated that the control parameters may control other parametersused in obtaining the various images.

FIG. 6 is diagrammatic illustration of a series of frames correspondingto the method of FIG. 4, and to the timing diagram of FIG. 5, showingthe capture of the image, determining the new control parameter, and theuse of new parameter in subsequent capture of an image. In FIG. 6, twoseparate and/or decoupled tracks are illustrated, for example, one trackcorresponding to where the decodable image is illuminated and the othertrack were the decodable image is not illuminated. For example, theindicia reading terminal may provide illumination periods of about 500microseconds, and periods of unillumination of about 5 to about 15milliseconds. It will be appreciated that the indicia reading terminalmay employ two separate autoexposure algorithms, one of which isoptimized for reading bar codes on paper and would run with frames whichhave the illumination on, and the other which is optimized for readingbar codes off screen such as a cell phone display would run with theframes that have the illumination off. The indicia reading terminal inthis example includes a two frame pipeline. When an exposure is set as aresult of information gleaned from frame X, it takes effect in frameX+1, but the result is only seen in image X+2. Same is said for exposurebeing set as a result of information gleaned from frame X+1, it takeseffect in frame X+2, but the result is only seen in image X+3. Afull-frame shutter imager can handle significant jumps in exposure fromframe to frame, so the two exposure routines can run interleaved with,but completely decoupled from, each other.

From the present description, it will be appreciated that a separate anddecoupled third, fourth, or more tracks may be implemented in accordancewith the preset invention. For example, a third track may employillumination subsystem at a reduced energization value. It will furtherbe appreciated that the indicia reading terminal of the presentinvention may also determine or calculate more than one controlparameter, which determined or calculated control parameters are used ina subsequent capture of an image.

It should also be appreciated that the image control parameter may beinternal operating parameters of the imager, for example, an exposureperiod value, a gain control value, a frame rate value, a gamma value,filtering coefficients or other suitable control parameters. However, itmay also be used for external control parameters used for imaging suchas illumination control, focus adjustment, aperture adjustment, or otherfunctions which can influence how image data is captured and/oranalyzed.

The image control parameter may be, for example, determined based on analgorithm. The process of receiving or capturing a frame of image data(i.e., 1D or 2D symbology, text, image, or other indicia) that meets thethreshold criteria of signal contrast, brightness, focus or other imagecharacteristics utilized by the imager control algorithm willhereinafter be referred to as obtaining an acceptable image. Thus, anacceptable image is one that falls within a configured tolerance of thetarget image requirements set forth by the algorithm. There are manyfactors that can affect how acceptable images are obtained. For example,the level of ambient lighting in the imaging environment, the distanceof the object from the imager, the contrast characteristics of theobject, and others can affect the quality of the acquired image. Thequality of the imager control algorithm in an image reader can be gaugedby its ability to utilize multiple configuration settings and adaptitself to a variety of imaging situations while acquiring acceptableimages. Thus, the quality of the imager control algorithm can be furthermeasured by how quickly the algorithm is able to configure the imager totake acceptable images in any given scanning environment.

For example, the algorithm may monitor or evaluate the brightness of thepixels such as the top 5 percent of the pixels. If the pixels aredetermined to be too bright, the length of time of exposure controlparameter may be lowered in obtaining a subsequent image. If the pixelsare determined to be too dark, the length of time of exposure controlparameter may be increased in obtaining a subsequent image.

As noted above, the control parameter of one track may include a firstalgorithm and the control parameter of the second track may include asecond algorithm. The first and second control parameter may bedifferent and/or the first and second control parameters may be the samebut have different values. Further algorithms for use in the presentinvention include the algorithms described in U.S. Pat. No. 7,874,485issued to Meier et al. entitled “Adaptive Optical Image Reader”, andU.S. Pat. No. 7,148,923 issued to Harper et al. entitled “Methods andApparatus for Automatic Exposure Control, the entire contents of thesepatents being incorporated herein by reference.

In one embodiment, terminal 1000 (FIG. 1) may be adapted to avoidsubjecting a frame of image data to a decode attempt unless the frame isdetermined to be of suitable quality for a decode attempt. Referringagain to the timing diagram of FIG. 5, in which a specific example isillustrated, CPU 1060 (FIG. 2) may not commence decoding processing, inaccordance with a decode processing thread at decode attempt processingperiod 5500 with respect to a particular frame, until evaluation of aparticular frame is determined to be of suitable quality for a decodeattempt as a result of processing occurring during processing such asperiod 5410, 5415, 5430, etc. While terminal 1000 (FIG. 1) may beoperative to subject each frame of a succession of frames to imagequality evaluation processing and select a subset of the succession offrames to decoding processing, it will be appreciated that not everyframe need be evaluated. For example, when one of the tracks (e.g., withillumination) of images provides a higher quality evaluation than theother track (e.g., without illumination), only one track may besubsequently evaluated. The evaluation of the image quality may becompared to predetermined criteria and/or to a prior image quality forthe track of images. A quality score above a threshold predeterminedcriteria or above a prior image quality may result in the frame imagesbeing processed for decoding by processor 1060 (FIG. 2). Various filtersmay be employed for processing the quality of the image frames.Filtering may employ an IQ filter. Other processing filters incorporablein the preset invention may include U.S. Patent Application PublicationNo. 2010/0108769 and U.S. Patent Application Publication No.2010/0108769 both by Wang et al., the entire subject matter of theseapplications being incorporated herein by reference. A successfuldecoding of the indicia based on one or more selected image frames mayterminate the scanning by terminal 1000.

With reference again to FIG. 2, indicia reading terminal 1000 mayinclude an image sensor 1032 comprising a multiple pixel image sensorarray 1033 having pixels arranged in rows and columns of pixels,associated column circuitry 1034 and row circuitry 1035. Associated withthe image sensor 1032 can be amplifier circuitry 1036 (amplifier), andan analog to digital converter 1037 which converts image information inthe form of analog signals read out of image sensor array 1033 intoimage information in the form of digital signals. Image sensor 1032 canalso have an associated timing and control circuit 1038 (incorporatingthe control parameter algorithms described above) for use in controllinge.g., the exposure period of image sensor 1032, gain applied to theamplifier 1036, etc. The noted circuit components 1032, 1036, 1037, and1038 can be packaged into a common image sensor integrated circuit 1040.Image sensor integrated circuit 1040 can incorporate fewer than thenoted number of components.

In one example, image sensor integrated circuit 1040 can be providede.g., by an MT9V022 (752×480 pixel array) or an MT9V023 (752×480 pixelarray) image sensor integrated circuit available from Micron Technology,Inc. In one example, image sensor array 1033 can be a hybrid monochromeand color image sensor array having a first subset of monochrome pixelswithout color filter elements and a second subset of color pixels havingcolor sensitive filter elements. In one example, image sensor integratedcircuit 1040 can incorporate a Bayer pattern filter, so that defined atthe image sensor array 1033 are red pixels at red pixel positions, greenpixels at green pixel positions, and blue pixels at blue pixelpositions. Frames that are provided utilizing such an image sensor arrayincorporating a Bayer pattern can include red pixel values at red pixelpositions, green pixel values at green pixel positions, and blue pixelvalues at blue pixel positions. In an embodiment incorporating a Bayerpattern image sensor array, processor 1060 prior to subjecting a frameto further processing can interpolate pixel values at frame pixelpositions intermediate of green pixel positions utilizing green pixelvalues for development of a monochrome frame of image data.Alternatively, processor 1060 prior to subjecting a frame for furtherprocessing can interpolate pixel values intermediate of red pixelpositions utilizing red pixel values for development of a monochromeframe of image data. Processor 1060 can alternatively, prior tosubjecting a frame for further processing interpolate pixel valuesintermediate of blue pixel positions utilizing blue pixel values. Animaging subsystem of terminal 1000 can include image sensor 1032 and alens assembly 200 for focusing an image onto image sensor array 1033 ofimage sensor 1032.

In the course of operation of terminal 1000, image signals can be readout of image sensor 1032, converted, and stored into a system memorysuch as RAM 1080. A memory 1085 of terminal 1000 can include RAM 1080, anonvolatile memory such as EPROM 1082 and a storage memory device 1084such as may be provided by a flash memory or a hard drive memory. In oneembodiment, terminal 1000 can include processor 1060 which can beadapted to read out image data stored in memory 1080 and subject suchimage data to various image processing algorithms. Terminal 1000 caninclude a direct memory access unit (DMA) 1070 for routing imageinformation read out from image sensor 1032 that has been subject toconversion to RAM 1080. In another embodiment, terminal 1000 can employa system bus providing for bus arbitration mechanism (e.g., a PCI bus)thus eliminating the need for a central DMA controller. A skilledartisan would appreciate that other embodiments of the system busarchitecture and/or direct memory access components providing forefficient data transfer between the image sensor 1032 and RAM 1080 arewithin the scope and the spirit of the invention.

With reference still to FIG. 2 and referring to further aspects ofterminal 1000, imaging lens assembly 200 can be adapted for focusing animage of decodable indicia 15 located within a field of view 1240 on asubstrate or on a screen onto image sensor array 1033. A size in targetspace of a field of view 1240 of terminal 1000 can be varied in a numberof alternative ways. A size in target space of a field of view 1240 canbe varied, e.g., by changing a terminal to target distance, changing animaging lens assembly setting, changing a number of pixels of imagesensor array 1033 that are subject to read out. Imaging light rays canbe transmitted about imaging axis 25. Lens assembly 200 can be adaptedto be capable of multiple focal lengths and multiple planes of optimumfocus (best focus distances).

Terminal 1000 may include an illumination subsystem 800 for illuminationof target, and projection of illumination pattern 1260. Illuminationpattern 1260, in the embodiment shown can be projected to be proximateto but larger than an area defined by field of view 1240, but can alsobe projected in an area smaller than an area defined by field of view1240. Illumination subsystem 800 can include a light source bank 500,comprising one or more light sources. Light source assembly 800 mayfurther include one or more light source banks, each comprising one ormore light sources, for example. Such light sources can illustrativelyinclude light emitting diodes (LEDs), in an illustrative embodiment.LEDs with any of a wide variety of wavelengths and filters orcombination of wavelengths or filters may be used in variousembodiments. Other types of light sources may also be used in otherembodiments. The light sources may illustratively be mounted to aprinted circuit board. This may be the same printed circuit board onwhich an image sensor integrated circuit 1040 having an image sensorarray 1033 may illustratively be mounted.

Terminal 1000 can also include an aiming subsystem 600 for projecting anaiming pattern (not shown). Aiming subsystem 600 which can comprise alight source bank can be coupled to aiming light source bank power inputunit 1208 for providing electrical power to a light source bank ofaiming subsystem 600. Power input unit 1208 can be coupled to system bus1500 via interface 1108 for communication with processor 1060.

In one embodiment, illumination subsystem 800 may include, in additionto light source bank 500, an illumination lens assembly 300, as is shownin the embodiment of FIG. 2. In addition to or in place of illuminationlens assembly 300 illumination subsystem 800 can include alternativelight shaping optics, e.g. one or more diffusers, mirrors and prisms. Inuse, terminal 1000 can be oriented by an operator with respect to atarget, (e.g., a piece of paper, a package, a screen, or another type ofsubstrate, etc.) bearing decodable indicia 15 in such manner thatillumination pattern 1260 is projected on decodable indicia 15. Inanother use, terminal 1000 can be oriented by an operator with respectto a target (backlit screen, LCD monitor, cathode ray tube, etc.)bearing decodable indicia 115 (FIG. 1) in such a manner that the targetsubstrate is self illuminating. In this case, an illumination patterngenerated by illumination subsystem 800 is not needed. In the example ofFIG. 2, decodable indicia 15 is provided by a 1D bar code symbol.Decodable indicia 15 could also be provided by a 2D bar code symbol oroptical character recognition (OCR) characters. Referring to furtheraspects of terminal 1000, lens assembly 200 can be controlled with useof electrical power input unit 1202 which provides energy for changing aplane of optimum focus of lens assembly 200. In one embodiment, anelectrical power input unit 1202 can operate as a controlled voltagesource, and in another embodiment, as a controlled current source.Electrical power input unit 1202 can apply signals for changing opticalcharacteristics of lens assembly 200, e.g., for changing a focal lengthand/or a best focus distance of (a plane of optimum focus of) lensassembly 200. Light source bank electrical power input unit 1206 canprovide energy to light source bank 500. In one embodiment, electricalpower input unit 1206 can operate as a controlled voltage source. Inanother embodiment, electrical power input unit 1206 can operate as acontrolled current source. In another embodiment electrical power inputunit 1206 can operate as a combined controlled voltage and controlledcurrent source. Electrical power input unit 1206 can change a level ofelectrical power provided to (energization level of) light source bank500, e.g., for changing a level of illumination output by light sourcebank 500 of illumination subsystem 800 for generating illuminationpattern 1260.

In another aspect, terminal 1000 can include power supply 1402 thatsupplies power to a power grid 1404 to which electrical components ofterminal 1000 can be connected. Power supply 1402 can be coupled tovarious power sources, e.g., a battery 1406, a serial interface 1408(e.g., USB, RS232), and/or AC/DC transformer 1410).

Further regarding power input unit 1206, power input unit 1206 caninclude a charging capacitor that is continually charged by power supply1402. Power input unit 1206 can be configured to output energy within arange of energization levels. An average energization level ofillumination subsystem 800 during exposure periods with the firstillumination and exposure control configuration active can be higherthan an average energization level of illumination and exposure controlconfiguration active.

Terminal 1000 can also include a number of peripheral devices includingtrigger 1220 (FIG. 1) which may be used to make active a trigger signalfor activating frame readout and/or certain decoding processes. Terminal1000 can be adapted so that activation of trigger 1220 activates atrigger signal and initiates a decode attempt. Specifically, terminal1000 can be operative so that in response to activation of a triggersignal, a succession of frames can be captured by way of read out ofimage information from image sensor array 1033 (typically in the form ofanalog signals) and then storage of the image information afterconversion into memory 1080 (which can buffer one or more of thesuccession of frames at a given time). Processor 1060 can be operativeto subject one or more of the succession of frames to a decode attempt.

For attempting to decode a bar code symbol, e.g., a one dimensional barcode symbol, processor 1060 can process image data of a framecorresponding to a line of pixel positions (e.g., a row, a column, or adiagonal set of pixel positions) to determine a spatial pattern of darkand light cells and can convert each light and dark cell patterndetermined into a character or character string via table lookup. Wherea decodable indicia representation is a 2D bar code symbology, a decodeattempt can comprise the steps of locating a finder pattern using afeature detection algorithm, locating matrix lines intersecting thefinder pattern according to a predetermined relationship with the finderpattern, determining a pattern of dark and light cells along the matrixlines, and converting each light pattern into a character or characterstring via table lookup.

Terminal 1000 can include various interface circuits for couplingvarious of the peripheral devices to system address/data bus (systembus) 1500, for communication with processor 1060 also coupled to systembus 1500. Terminal 1000 can include interface circuit 1028 for couplingimage sensor timing and control circuit 1038 to system bus 1500,interface circuit 1102 for coupling electrical power input unit 1202 tosystem bus 1500, interface circuit 1106 for coupling illumination lightsource bank power input unit 1206 to system bus 1500, and interfacecircuit 1120 for coupling trigger 1220 to system bus 1500. Terminal 1000can also include a display 1222 coupled to system bus 1500 and incommunication with processor 1060, via interface 1122, as well aspointer mechanism 1224 in communication with processor 1060 viainterface 1124 connected to system bus 1500. Terminal 1000 can alsoinclude range detector unit 1210 coupled to system bus 1500 viainterface 1110. In one embodiment, range detector unit 1210 can be anacoustic range detector unit. Various interface circuits of terminal1000 can share circuit components. For example, a common microcontrollercan be established for providing control inputs to both image sensortiming and control circuit 1038 and to power input unit 1206. A commonmicrocontroller providing control inputs to circuit 1038 and to powerinput unit 1206 can be provided to coordinate timing between imagesensor array controls and illumination subsystem controls.

A succession of frames of image data that can be captured and subject tothe described processing can be full frames (including pixel valuescorresponding to each pixel of image sensor array 1033 or a maximumnumber of pixels read out from image sensor array 1033 during operationof terminal 1000). A succession of frames of image data that can becaptured and subject to the described processing can also be “windowedframes” comprising pixel values corresponding to less than a full frameof pixels of image sensor array 1033. A succession of frames of imagedata that can be captured and subject to the above described processingcan also comprise a combination of full frames and windowed frames. Afull frame can be read out for capture by selectively addressing pixelsof image sensor 1032 having image sensor array 1033 corresponding to thefull frame. A windowed frame can be read out for capture by selectivelyaddressing pixels of image sensor 1032 having image sensor array 1033corresponding to the windowed frame. In one embodiment, a number ofpixels subject to addressing and read out determine a picture size of aframe. Accordingly, a full frame can be regarded as having a firstrelatively larger picture size and a windowed frame can be regarded ashaving a relatively smaller picture size relative to a picture size of afull frame. A picture size of a windowed frame can vary depending on thenumber of pixels subject to addressing and readout for capture of awindowed frame.

Terminal 1000 can capture frames of image data at a rate known as aframe rate. A typical frame rate is 60 frames per second (FPS) whichtranslates to a frame time (frame period) of 16.6 ms. Another typicalframe rate is 30 frames per second (FPS) which translates to a frametime (frame period) of 33.3 ms per frame. A frame rate of terminal 1000can be increased (and frame time decreased) by decreasing of a framepicture size.

Further aspects of terminal 1000 in one embodiment are described withreference again to FIG. 1. Trigger 1220, display 1222, pointer mechanism1224, and keyboard 1226 can be disposed on a common side of a hand heldhousing 1014 as shown in FIG. 1. Display 1222 and pointer mechanism 1224in combination can be regarded as a user interface of terminal 1000.Display 1222 in one embodiment can incorporate a touch panel fornavigation and virtual actuator selection in which case a user interfaceof terminal 1000 can be provided by display 1222. A user interface ofterminal 1000 can also be provided by configuring terminal 1000 to beoperative to be reprogrammed by decoding of programming bar codesymbols. A hand held housing 1014 for terminal 1000 can in anotherembodiment be devoid of a display and can be in a gun style form factor.Imaging module 1040 including image sensor array 1033 and imaging lensassembly 200 can be incorporated in hand held housing 1014.

While the present invention has been described with reference to anumber of specific embodiments, it will be understood that the truespirit and scope of the invention should be determined only with respectto claims that can be supported by the present specification. Further,while in numerous cases herein wherein systems and apparatuses andmethods are described as having a certain number of elements it will beunderstood that such systems, apparatuses and methods can be practicedwith fewer than the mentioned certain number of elements. Also, while anumber of particular embodiments have been described, it will beunderstood that features and aspects that have been described withreference to each particular embodiment can be used with each remainingparticularly described embodiment.

1. A device for obtaining images, said device comprising: an imagingsubsystem comprising an image sensor array and an imaging assemblyoperative for focusing an image onto said image sensor array; a housingincorporating said imaging subsystem; wherein said device is adapted toacquire a first plurality of images based on a first control parameterin which said first control parameter for a subsequent image of saidfirst plurality of images is adjusted based on a prior image of saidfirst plurality of images, and adapted to acquire a second plurality ofimages based on a second control parameter in which said second controlparameter for a subsequent image of said second plurality of images isadjusted based on a prior image of said second plurality of images,adjustment of said first control parameter being determined differentlycompared to adjustment of said second control parameter; and whereinacquisition of said first plurality of images being interspersed withand obtained generally concurrently with acquisition of said secondplurality of images, and acquisition of said first plurality of imagesand adjustment of said first control parameter being separate fromacquisition of said second plurality of images and adjustment of saidsecond control parameter.
 2. The device of claim 1 further comprisingsaid device being operable to attempt to decode a decodable indiciautilizing one or more images of said first and second plurality ofimages.
 3. The device of claim 1 further comprising an illuminationsubsystem operative for projecting an illumination pattern operable foruse in acquiring said first plurality of images and said secondplurality of images.
 4. The device of claim 1 wherein said firstplurality of images and said second plurality of images being evenlyinterspersed so that said first control parameter obtained at image N isutilized in image N+2, and so that said second control parameterobtained at image N+1 is utilized in image N+3.
 5. The device of claim 1wherein said first control parameter and said second control parametercomprises the same control parameter having different values.
 6. Thedevice of claim 1 wherein said first control parameter comprises a firstexposure control parameter, and said second control parameter comprisesa second exposure control parameter.
 7. The device of claim 1 whereinsaid device is operable to determine quality evaluation based on qualityof pixel data of at least one of said images of said first plurality ofimages and said second plurality of images.
 8. The device of claim 6further comprising said device being operable to attempt to decode adecodable indicia from selected images based on said quality evaluation.9. The device of claim 1 wherein said device is operable to attempt todecode the decodable indicia comprising a bar code.
 10. The device ofclaim 1 wherein said device is operable to attempt to decode a decodableindicia comprising at least one of a bar code disposed on a substrate,and a bar code disposed on a backlit display.
 11. The device of claim 1wherein said device comprises a hand held indicia reading terminal. 12.An indicia reading terminal comprising: an illumination subsystemoperative for projecting an illumination pattern; an imaging subsystemcomprising an image sensor array and an imaging assembly operative forfocusing an image onto said image sensor array; a housing incorporatingsaid illumination subsystem and said imaging subsystem; wherein saidindicia reading terminal is adapted to acquire a first plurality ofimages exposed during illuminated portions of said illumination patternbased on a first control parameter in which said first control parameterfor a subsequent image of said first plurality of images is adjustedbased on a prior image of said first plurality of images, and adapted toacquire a second plurality of images exposed during unilluminatedportions of said illumination pattern based on a second controlparameter in which said second control parameter for a subsequent imageof said second plurality of images is adjusted based on a prior image ofsaid second plurality of images; wherein acquisition of said firstplurality of images being interspersed with and being obtained generallyconcurrently with acquisition of said second plurality of images, andacquisition of said first plurality of images and adjustment of saidfirst control parameter being separate from acquisition of said secondplurality of images and adjustment of said second control parameter; andwherein said indicia reading terminal is operable to attempt to decode adecodable indicia comprising a bar code disposed on a substrate using atleast one of said first plurality of images, and operable to attempt todecode a decodable indicia comprising a bar code disposed on a backlitdisplay using at least one of said second plurality of images.
 13. Theindicia reading terminal of claim 12 wherein said first plurality ofimages and said second plurality of images being evenly interspersed sothat a first control parameter obtained at image N is utilized in imageN+2, and so that a second control parameter obtained at image N+1 isutilized in image N+3.
 14. The indicia reading terminal of claim 12wherein said first image control parameter and said second image controlparameter comprises the same image control parameter having differentvalues.
 15. The indicia reading terminal of claim 12 wherein said firstcontrol parameter comprises a first exposure control parameter, and saidsecond control parameter comprises a second exposure control parameter.16. The indicia reading terminal of claim 12 wherein said indiciareading terminal is operable to determine quality evaluation of at leastone of said images of said first plurality of images and said secondplurality of images, and wherein said indicia reading terminal beingoperable to attempt to decode the decodable indicia comprises saidindicia reading terminal being operable to attempt to decode a decodableindicia from selected images based on said quality evaluation.
 17. Theindicia reading terminal of claim 12 wherein said indicia readingterminal comprises a hand held indicia reading terminal.
 18. A methodfor use in obtaining images, the method comprising: automaticallyadjusting a first control parameter in a device for capturing a firstplurality of images; and automatically adjusting a second controlparameter in the device for capturing a second plurality of images suchthat automatic adjustment of the first control parameter is interspersedwith, separate from, and obtained generally concurrently with theautomatic adjustment of the second control parameter, and adjustment ofthe first control parameter being determined differently compared toadjustment of the second control parameter.
 19. The method of claim 18further comprising attempting to decode the decodable indicia utilizingone or more images of the first and second plurality of images.
 20. Themethod of claim 18 further comprising providing an illumination patternoperable for use in acquiring said first plurality of images and saidsecond plurality of images.
 21. The method of claim 18 wherein the firstplurality of images and the second plurality of images being evenlyinterspersed so that a first control parameter obtained at image N isutilized in image N+2, and so that a second control parameter obtainedat image N+1 is utilized in image N+3.
 22. The method of claim 18wherein the first control parameter and the second control parametercomprises the same control parameter having different values.
 23. Themethod of claim 18 wherein said first control parameter comprises afirst exposure control parameter, and said second control parametercomprises a second exposure control parameter.
 24. The method of claim18 wherein the first plurality of images is adapted to decodingdecodable indicia disposed on a substrate, and the second plurality ofimages is adapted to decoding decodable indicia disposed on a backlitdisplay.
 25. The method of claim 18 further comprising determining aquality evaluation of at least one of the images of the first pluralityof images and the second plurality of images, and further comprisingattempting to decode decodable indicia utilizing one or more imagesselected from images based on the quality evaluation.
 26. The method ofclaim 18 wherein the decodable indicia comprising a bar code.
 27. Amethod for decoding decodable indicia, the method comprising: projectingan illumination pattern from an indicia reading terminal onto adecodable indicia; automatically adjusting a first control parameter inthe indicia reading terminal for capturing a first plurality of imagesexposed during illuminated portions of the illumination pattern;automatically adjusting second control parameter in the indicia readingterminal for capturing a second plurality of images exposed duringunilluminated portions of the illumination pattern such that automaticadjustment of the first control parameter is interspersed with andobtained generally concurrently with the automatic adjustment of thesecond control parameter; and attempting to decode the decodable indiciautilizing one or more images of the first and second plurality ofimages.
 28. The method of claim 27 wherein the first plurality of imagesand the second plurality of images being evenly interspersed so that afirst control parameter obtained at image N is utilized in image N+2,and so that a second control parameter obtained at image N+1 is utilizedin image N+3.
 29. The method of claim 27 further comprising optimizingthe control parameter for images exposed during the illuminated portionsof the illumination pattern for decoding the decodable indicia disposedon a substrate, and optimizing the control parameter for the imagesexposed during unilluminated portions of the illumination pattern fordecoding the decodable indicia disposed on a backlit display.
 30. Themethod of claim 27 wherein the first image control parameter and thesecond image control parameter comprises the same image controlparameter having different values.
 31. The method of claim 27 whereinsaid first control parameter comprises a first exposure controlparameter, and said second control parameter comprises a second exposurecontrol parameter.
 32. The method of claim 27 further comprisingdetermining a quality evaluation of at least one of the images of thefirst plurality of images and the second plurality of images, andwherein the attempting to decode comprises attempting to decodedecodable indicia utilizing one or more images selected from imagesbased on the quality evaluation.